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Do I have to sign up for Medicare at 65 if I am still working?

Usually no if your employer has 20 or more employees. If it has fewer than 20, you generally need Part B at 65, because Medicare pays first.

Updated September 3, 2026 · 4 min read · by Gerino Alejos

Usually no. If your employer has 20 or more employees and you are covered by its health plan, you can wait on Part B without a late penalty for as long as you keep working. Part B is the part of Medicare that pays for doctor visits and outpatient care, and the penalty is an extra charge added to its monthly bill. If the company has fewer than 20 employees, you generally need to take Part B at 65, because Medicare pays first. Medicare explains how working past 65 affects your timing on medicare.gov.

If your employer has 20 or more employees

Your group health plan, the plan you get through your job, pays first and Medicare pays second. You can generally delay Part B without any penalty for as long as you are actively working and covered by that plan.

When the job or the coverage ends, you get a Special Enrollment Period, which is a window to sign up late without a penalty. It lasts eight months, counted from the end of employment or the end of the coverage, whichever comes first.

Most people in this situation still take Part A at 65, the part of Medicare that pays for hospital stays, because it usually costs nothing. There is one important exception, covered below.

If your employer has fewer than 20 employees

Now Medicare pays first and your group plan pays second. If you do not enroll in Part B, your group plan can pay as if Medicare had already covered its share. You are left holding the difference.

Small employers are common in South Texas, so this applies to a lot of people. In this case you generally need to take Part B at 65. Ask your HR department or your plan administrator to confirm in writing how the plan coordinates with Medicare, meaning which one pays first. Do not rely on a spoken answer.

Why Part A stops your HSA contributions

If you put money into a Health Savings Account (HSA), which is a savings account for medical costs that comes with tax breaks, this matters. Almost nobody hears about it in time.

Once you are enrolled in any part of Medicare, including premium free Part A, you can no longer put money into an HSA. There is a second problem. When you file for Social Security or Medicare after 65, Part A can be backdated up to six months. Any HSA contributions made during those backdated months count as excess contributions, and you pay tax on them.

Coverage that does not count as employer coverage

Some coverage feels like employer insurance but does not protect you from the penalty. Delaying Part B because you have any of these is a mistake.

• COBRA, the coverage that lets you keep your old employer plan for a while after leaving a job. It is not coverage from active employment, and your enrollment clock is already running.
• Retiree coverage from a former employer. Same problem.
• A Marketplace plan from HealthCare.gov.
• Your spouse's plan, if that spouse is retired rather than actively working.

The rule is active employment, either yours or your spouse's, not simply having other insurance. See whether you need Medicare with employer insurance.

Part D while you are still working

Part D is the part of Medicare that pays for prescriptions, and it has its own separate penalty. Your employer plan should send you a notice each year saying whether its drug coverage is creditable, meaning at least as good as Part D.

Keep those notices. If your coverage is creditable, you can delay Part D safely. If it is not, the penalty starts adding up whether anyone told you or not.

What to do before your 65th birthday

1. Ask HR for the employee count and for written confirmation of how the plan coordinates with Medicare.
2. Find the creditable coverage notice for your drug plan and keep it.
3. If you fund an HSA, pick your stop date at least six months ahead.
4. Set a reminder for three months before you retire, not the week of.

If the answer is still not clear after that, call our office in McAllen and we will go through it with you. See how the penalty is calculated to see what is at stake.

If you are turning 65 and want a head start before that call, see your Medicare options. Enter your ZIP code and a licensed agent calls you back, usually the same business day.

Gerino Alejos

Licensed insurance agent · License 3128710 · NPN 18243381

Owner of McAllen Insurance Group, an independent agency on North 10th Street in McAllen. Works with clients across Hidalgo, Cameron and Starr counties on Medicare, Marketplace health, life and auto coverage. Se habla español.